Our renewal grant will extend our previous work on the control of aldosterone secretion in normal and hypertensive man and further investigate the control of sodium excretion. Methods have been or are being developed in our lab for the measurement of plasma aldosterone, renin, and prostaglandins A1 and A2 by radioimmunoassay in peripheral and renal blood. We shall extend our observation that prostaglandin may be a control mechanism for alsosterone secretion in man (Circ Res, 21:II-19, 1973). Additionally, with the development in our lab of radioimmunoassay for PGA1 and PGA2, we will study the physiology of peripheral and renal PGA and PGE in hypertension and sodium metabolism. Bibliographic references: Fichman, M, Michalakis, A., and R. Horton. Regulation of aldosterone in the syndrome of inappropriate ADH secretion. J. Clin. Endoc. 39:136, 1974; Golub, M., Zia. P., Matsuno, M., and R. Horton. Metabolism of prostagladins A and E in man. J. Clin. Invest. (submitted May 1975).